Heian M9205B Router Spindle Failure
Heian M9205B router spindle, 17,000 RPM, oil mist bearing lubrication, stator drive
This spindle from a 4-head bridge type CNC router arrived with fine sawdust packed into every external orifice. It had also penetrated the spindle interior, contaminating the front bearings and causing them to fail. The BT-35 tooling taper was also heavily worn with >30µ runout, the drive dogs (keys) were worn and the incoming tool retention force was extremely low. We also discovered that the OD of the front & rear bearing journals of the shaft were worn undersized & fretted where the bearings locate, and both the front & rear housing ID’s were worn oversized.
Our first task in this rebuild was to grind, chrome plate and finish grind the tooling taper, both bearing journals and both the front & rear housings. The taper runout was reduced to <2µ. We reworked the light damage to the drive dogs and reassembled the spindle with all new bearings, Bellevilles, gripper balls, preload springs, seals and assembly hardware. After the spindle was completed and good drawbar force was obtained, we test ran it for four hours while trim balancing it and confirming good vibration & thermal characteristics.